Optical systems for theatrical and stage lighting fixtures are generally intended to capture light from a light source that emits light over a wide angle and produce a narrower beam of focused or unfocused light. Existing optical systems used in related fields include ellipsoidal reflectors in combination with aspheric lenses and parabolic reflectors optionally in combination with Fresnel lenses.
In general, the optical systems are composed of illumination and imaging stages. The illumination stage is comprised of a light source and optical component(s) that gather the light into a narrower converging or diverging beam. The imaging stage has one or more elements that relay an image plane to a far-field target. The effectiveness of these systems is a function of the etendue of the light source and the limits of aperture and acceptance angle of the subsequent optical components.
State of the art architectural theatrical and stage lighting fixtures employ conventional light sources such as gas-discharge or incandescent lamps. Typically the etendue of a conventional light source at a given level of luminous flux is significantly better than light emitting diodes (LED), but conventional light sources have drawbacks such as lower luminous efficacy, shorter operating lifetime, and less robust package. Thus, there is a need for an optical system that overcomes the etendue limitations of an LED for effective application.